Towers and other structures made from structural steel are commonly used in various industries, such as, for example, refineries, petrochemical plants, and the like. The fabrication of such structures from structural steel is complicated by the use of personnel fall restraint devices which are increasingly popular with a general desire for improved personnel safety. Steel-workers at elevations substantially above ground employ safety belts, harnesses and the like which are awkward to use, particularly when the worker must traverse a joint or other obstruction which prevents passage of the restraint device attachment. In addition, as the structural steel structure is erected, there are initially at least no handrails positioned for the safety of the worker.
The prior art steel structures are generally erected by welding and/or bolting various structural members such as columns and crossbeams together. Diagonal and knee bracing is generally required to adequately strengthen the structure. Considerable effort is also involved in accurate placement and leveling of the structure. In addition, when it is desired to demolish the conventional structural steel structures, it is necessary to unbolt and cut the structural steel members. Moreover, such demolition can be dangerous and expensive.
Concrete structures have sometimes been employed, but these are rarely encountered in the petrochemical industry. Steel structures are generally chosen because they are relatively inexpensive to fabricate and erect, and are more readily modified after installation when the need arises. Nonetheless, various modular concrete constructions, which generally employ concrete slabs as opposed to structural steel members, are known and used, especially in the high rise building industry. Examples of this art are found in U.S. Pat. Nos. 4,330,970 to Bonink; 3,827,203 to Berrie; 3,378,931 to Singer et al.; 3,429,092 to Perry et al.; and 4,640,070 to Moffat.
Bonink discloses a design utilizing single column members equipped with up to four vertical pipes which function as dowels to interlock with framing beams. However, this design is intended to provide some degree of dimensional flexibility for the concrete structures. Thus, this construction requires grouting in the voids of the framing beams in which the pipes or dowels are received. This would also appear to complicate disassembly of the structure.
Use of the Berrie construction design is not readily adaptable to structural steel erection. This design requires complicated beam-to-column connections which would make preassembly and erection of floor sections in structural steel structures difficult at best.
From U.S. Pat. No. 3,378,971 to Singer et al., it is known to use a joint member in a floor or roof member of a building wherein the roof or floor is a slab and the joint is a tapered spigot and socket joint to effect a rigid distortion-resistant connection between the slab and the column. The spigot is coaxial with each column and requires a column for each corner of a floor panel. Structural strength in this design is achieved with a tight fit between the spigot and corresponding socket formed in the floor panel.
From U.S. Pat. No. 3,429,092 to Perry et al., it is known to use preformed concrete columns and beams by using axially extending connector spindles and radially extending collar means to support and connect succeeding column tiers.
From U.S. Pat. No. 4,640,070 to Moffat it is known to use support columns which are brought through the existing roof of a building in combination with a large platform truss supported thereon to support conventional construction built on the platform truss to add extra floors on existing buildings.
Modular construction has also been used in toy and model building sets, such as, for example, as described in U.S. Pat. Nos. 2,676,420 to Berg and 4,571,200 to Serna. Berg describes a model building construction comprising floor mat members which are perforated at the corners thereof and column members comprising, at one end a horizontal plate having a dowel member adapted to anchor to the floor member and a superimposed column member, and at the other end a flat plate member having an aperture adapted to receive the dowel member from the column therebelow. While this technique appears to work well with toy models, such a construction would not be structurally possible in full scale structural steel construction because it requires sandwich decking between column sections. Similar structures in steel construction such as steel grating or fiberglass reinforced plastic grating, would fail under such circumstances. The Serna reference has similar drawbacks.